THE 11U0W N-T All, MOTH. I 19 
out entering the adjoining property. Permission to do so 
was refused. As a result this branch and another tree 
(Fig. 32, c) on the untreated property was defoliated, while 
the rest of the tree (Fig. 32, &), from which the nests had 
been removed, bore its normal foliage unmolested. 
Spraying. — While the caterpillars are young they may be 
effectively destroyed by spraying with arsenate of lead. 
The brown-tail caterpillars seem to be much more suscep- 
tible to the poison than those of the gipsy moth. Experi- 
ments made by us in the laboratory indicate that if sprayed 
while the caterpillars are young early in May arsenate 
of lead at the rate of three pounds per barrel of water 
should be sufficient, but if delayed until late in May or June 
1, when they are nearly full grown, five pounds per barrel 
should be used. 
When the eggs hatch in early August and the young 
caterpillars skeletonize the leaves prior to forming their 
winter webs (see figure 27), they may be readily killed 
by spraying with arsenate of lead or Paris Green. In 
the apple orchard there are numerous other caterpillars 
doing more or less damage to the foliage at this season 
which may be controlled by the same spraying, which there- 
fore becomes a practice to be commended. Experiments 
made by us show that not less than five pounds of arsenate 
of lead to a barrel of water should be used, and that an 
increase to ten pounds per barrel merely results in killing 
the caterpillars a day or two quicker. Arsenate of lead is 
preferred on account of its unusual adhesive properties, 
remaining on the foliage several weeks after hard rains. 
Paris Green is very much quicker in its effect and is, there- 
fore, to be preferred in some respects when there is no 
immediate prospect of rain. Care must be taken in the use 
of Paris Green that plenty of lime be added to prevent 
burning of the foliage, while arsenate of lead may be used 
in large quantities without danger in this regard. Our ex- 
periments indicate that a half pound of Paris Green per 
barrel will kill the caterpillars as quickly as ten pounds of 
arsenate of lead, but it does not follow, therefore, that 
Paris Green is to be preferred, as the other factors above 
mentioned must be considered. 
Experiments made during the past season show that by 
thorough spraying early in August the trees were practi- 
cally freed of the winter nests, while other trees in the 
same orchard were well covered with them. Furthermore, 
besides controlling the brown-tail moth, a number of com- 
